The present invention is related generally to an apparatus for detecting ambient lighting levels within a given area and, more particularly, to a system and method for controlling the lighting level of gas discharge lamps through the use of the detected ambient level of the light in the immediate vicinity of the lamps.
The use of photocell arrangement to detect the presence and/or intensity of light within a given area to control the energization of the light is well known in the art. Generally, the photocell is connected in a feedback loop of the circuitry, to cause increased or decreased energization of the lamp, and provide a stable or predetermined level of lighting output from the system. Examples of lighting systems incorporating such a photocell are shown by U.S. patent application Ser. No. 286,770 filed July 27, 1981, now U.S. Pat. No. 4,464,610, entitled Modular Lighting Control with Circulating Inductor; Ser. No. 309,260 filed Oct. 7, 1981, now U.S. Pat. No. 4,463,287, entitled Four Lamp Modular Lighting Control; Ser. No. 338,340 filed Jan. 11, 1982, now abandoned, entitled Magnetic Ballast with Thyristor Control; and Ser. No. 443,243 filed Nov. 22, 1982, now U.S. Pat. No. 4,437,043, entitled Lighting Control for High Intensity Discharge Lamp, all of which are assigned to the same assignee as the present application. Other manufacturers have also devised systems for detecting lighting intensity within a given area for use within an electrical circuit to control electrical power to a lighting system.
This invention is concerned with the mounting of a photocell arrangement for ready access to light in the immediate vicinity of the lighting system, and a particular construction of the photocell arrangement providing for ease of adjustment of the amount of light impinging upon the pohotocell.